Adolescent Knee Pain

Anterior knee pain is encountered frequently in clinical practice across all age groups. However, certain pathologies are age specific, and adolescents often present with difficulties that are unique to their growing bodies. The two conditions described here share close similarities and are seen most typically between the ages of 9 and 16. They are considered much more likely in boys but the incidence in girls has been increasing over the last couple of decades as they become more involved in high energy sports. Both 'Osgood Schlatter's Disease' and 'Sinding-Larsen-Johansson Syndrome' refer to repeated stresses of the patella tendon and its bony attachments, with a strong correlation seen in those participating in running and jumping sports. Both are considered self-limiting and in most cases will not cause symptoms later in life. Patello-femoral pain is also common in children and adolescents, more information of this can be found here.

'Why does my child have knee pain?'

We know that in childhood and adolescence our bones develop around centres of ossification known as ‘growth plates’. These areas of cartilage within the bone gradually produce bone cells as we mature. Usually by the late teens or very early 20’s, skeletal maturity has been achieved and we see the integration of these typical ossification centres into adult bone.

At the knee, the strong tractional pull of the quadriceps group acts through the growth plates of the patella tendon attachments. These growth plates exist at both the inferior pole (bottom tip) of the patella and at the insertion of the patella tendon into the tibial tuberosity. Often coinciding with growth spurts, repetitive stress of these areas caused by sports can lead to tendon inflammation, pain and tractional stress on the growth plate to the point where it may even separate from the main bone. As the growth plate tries to heal, it lays down additional cells, creating a characteristic (and fortunately painless) ‘bump’ that can remain clearly visible for the rest of your life. This is much more common in children who participate in vigorous running, jumping and kicking sports that require forceful recruitment of the quadriceps.

When this process affects the inferior pole of the patella, it is called Sinding-Larsen Johansson Syndrome (SLJS). It will usually affect a child between 10-13 years of age.

When this process affects the tibial tuberosity where the patella tendon attaches, it is called Osgood-Schlatter's Disease (OSD). It will usually affect an adolescent between 12-16 years of age but can persist longer than this in some.

Risk Factors

• Given the connection between forceful quadriceps contraction, skeletal immaturity and the onset of OSD and SLJS, it is not surprising that excess body weight and participation in ballistic running, jumping and kicking sports increase the risk. Perhaps due to their higher participation rate in such sports, the conditions occur 3-7 times more in boys than girls.
• Previous trauma has been variably reported in studies, but there does not appear to be any definitive link with this, with many developing insidiously and without specific cause.

Some Key Points:

• Most seen in active boys 12-15 years of age, but becoming more common in girls as well, though occurring earlier at an age of 11-13 years. Girls usually resolve sooner because they achieve greater skeletal maturity by around age 14.
• Most children affected are actively participating in sports such as basketball, football and gymnastics whilst simultaneously experiencing a growth spurt.
• 20-30% of cases involve bilateral symptoms, & up to 10% may have symptoms into adulthood.
• Acute symptoms will usually resolve in approximately 4-10 weeks, but often experience recurrent exacerbations through the teenage years.
• A prominent tibial tuberosity of varying size is the hallmark of OSD and does not resolve once formed. The tuberosity can be extremely tender to impact and kneel on.

How Can We Help?

Diagnosis is usually made clinically but plain radiographs can also be used, both to identify the magnitude of the problem in some, and to exclude alternative pathologies in others.

• ‘Relative’ Rest is advisable, though there is currently no evidence to suggest that complete avoidance of activity will hasten recovery. Indeed, stopping all exercise may be counter-productive as it can lead to secondary loss of fitness and strength generally. What is more important is a short term reduction in ballistic types of exercise that involve running, kicking and jumping. It is generally thought that cessation from training for 1-2 weeks with a gradual resumption back to full training within approximately 4-6 weeks is an effective ‘rule of thumb’ to follow. Obviously, this may vary with the severity of each case.
• R.I.C.E - Rest, Ice, Compression, Elevation. The fundamental principles of acute soft tissue injury management apply to these conditions and will help reduce pain and local swelling.
• Electrotherapy & Ultrasound: These modalities can be effective in managing acute symptoms in the short term, assisting with pain, inflammation, and tissue repair.
• Medication: Simple analgesia (e.g. paracetamol) is recommended, along with low level anti-inflammatory medication in those with more severe pain.
• Strapping & Braces may be used occasionally, particularly in more stubborn or difficult cases. Most of the time they are unnecessary unless there is an issue with a second simultaneous problem such as patello-femoral maltracking or tendinopathy. Patella tendon straps can be a useful tool in helping to deflect some of the stress away from the juvenile growth plates.
• Manual Therapy & Exercise: Establishing & maintaining appropriate strength and flexibility is an important consideration. Given the relationship between growth spurts and activity, biomechanical stresses can be amplified in the presence of muscular tightness, so appropriate education from a Physio can be very useful in the longer term and will help to mitigate the chances and extent of future exacerbations.